JP7737626B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device, and more specifically to a vehicle control device equipped with an ACC function.

As a driving assistance function, ACC (adaptive cruise control) has been put into practical use. If there is no preceding vehicle in the vehicle's lane, the vehicle will travel at a constant speed at a set speed, and if there is a preceding vehicle in the vehicle's lane traveling slower than the set speed, the vehicle will follow the preceding vehicle while maintaining a set time interval.

For example, Patent Document 1 discloses that a control device for a vehicle with an ACC function is equipped with a turning radius calculation means that calculates the turning radius of the vehicle itself, and an upper limit vehicle speed setting means that sets an upper limit vehicle speed according to the calculated turning radius, and controls the vehicle speed of the vehicle while turning so that it remains below the upper limit vehicle speed.

Japanese Patent Application Laid-Open No. 2008-68752

In a vehicle equipped with a stepped automatic transmission, when driving in ACC mode on a flat road with low running resistance or on a downhill slope and entering a sharp curve, the required torque may be significantly reduced to suppress acceleration, causing the vehicle to upshift. After that, when the required torque is increased to accelerate after passing the curve, the vehicle may downshift. This type of upshifting has the advantage of lowering engine speed and reducing fuel consumption, but if two gears are changed by upshifting or downshifting in an extremely short period of time, the change in driving force becomes significant, compromising the feel.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to improve the gear shift feeling when driving on curves in ACC mode in a vehicle equipped with a stepped automatic transmission.

In order to solve the above problems, the present invention provides:
A control device for a vehicle equipped with a stepped automatic transmission,
an ACC function that drives the vehicle at a set vehicle speed when there is no preceding vehicle in the vehicle's lane, and requests acceleration/deceleration to follow the preceding vehicle while maintaining a set inter-vehicle time when there is a preceding vehicle in the vehicle's lane;
a curve driving support function that requests deceleration when an approach to a curve with a predetermined curvature or more is detected and a curve driving condition is met;
In those having
The vehicle is characterized in that, when the curve driving condition is met while the vehicle is traveling using the ACC function, the upper limit of the gear shift of the automatic transmission is limited to one gear.

As described above, the vehicle control device of the present invention limits the upper limit of gear changes to one gear when entering a curve with a predetermined curvature or greater is detected during ACC driving. This avoids two-stage gear changes in an extremely short period of time even when a torque reduction request is issued due to a deceleration request, which is advantageous in improving the gear change feeling on curved sections.

FIG. 1 is a block diagram showing a vehicle cruise control system. 4 is a flowchart showing a gear shift control according to the first embodiment of the present invention. 10 is a flowchart showing a gear shift control according to a second embodiment of the present invention. FIG. 1 is a schematic diagram showing a road including a curve section.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, a vehicle 1 is equipped with an internal combustion engine 2 and a stepped automatic transmission 4 via a clutch 3 in a torque transmission path from the engine 2 to drive wheels (6).

The automatic transmission 4 is configured as an AMT (Automated Manual Transmission) type automatic transmission having an MT type shifting mechanism, for example, a parallel gear type shifting mechanism with constant mesh synchromesh, and a shift actuator that performs the gear stage changing operation, and is equipped with an AMT controller 40 that performs shifting operations by referring to a shift map (automatic shift line diagram) based on the vehicle speed and throttle opening .

The gear change actuator includes a select actuator that switches between P/R/N/D ranges and high/low gears depending on the operating position of a select lever (not shown), and a shift actuator that performs shift operations. It works in conjunction with the clutch actuator to perform gear changes, including clutch release, gear change, and clutch engagement.

The vehicle 1 is equipped with an engine controller 20 that controls the output of the engine 2 in response to the throttle opening (torque demand) provided by accelerator pedal operation (not shown) and acceleration/deceleration commands from the ACC controller 10 (described below). The AMT controller 40, through cooperative control with the engine controller 20, executes engine control linked to the clutch release/engagement operation during the above-mentioned gear shift operation.

The vehicle 1 is equipped with a brake system that constitutes an ABS/vehicle behavior stabilization device, which includes a brake controller 30 that can individually control the braking force of the brakes 36 on the left and right front wheels 6 and the brakes 37 on the left and right rear wheels 7 in response to brake pedal operation (not shown) or deceleration commands from the ACC controller 10 (described below), a brake actuator (hydraulic actuator) (not shown), wheel speed sensors 36 on the left and right front wheels 6, and wheel speed sensors 37 on the left and right rear wheels 7.

A vehicle 1 with the basic configuration described above is equipped with a preceding vehicle detection means 11, which, together with the ACC controller 10, constitutes an ACC system. The preceding vehicle detection means 11 can be one or more detection means, such as millimeter-wave radar, a monocular camera, a stereo camera, or LIDAR, that have the function of detecting the presence of a preceding vehicle or object (obstacle, structure) ahead of the host vehicle and can measure the relative distance (relative inter-vehicle time) between the host vehicle and the preceding vehicle or obstacle.

The ACC controller 10 is configured to issue acceleration/deceleration commands (torque requests/brake requests) to the engine controller 20 and brake controller 30 in place of the driver's accelerator/brake operation based on the detection information from the preceding vehicle detection means 11 and the vehicle speed calculated from the detection values of the wheel speed sensors 36, 37, and to execute adaptive cruise control (constant speed driving/follow-up driving control/deceleration/stop/restart control) compatible with all vehicle speed ranges.

That is, the brake controller 30, upon receiving a deceleration command from the ACC controller 10, issues a brake request (hydraulic pressure request) to the brake actuator and controls the braking force of the brakes 36, 37, thereby controlling the vehicle speed. Furthermore, upon receiving an acceleration/deceleration command (torque increase request/torque decrease request) from the ACC controller 10, the engine controller 20 controls the actuator output (throttle opening) of the engine 2, thereby controlling the torque of the engine 2 and controlling the vehicle speed.

Through the above control by the ACC controller 10, vehicle 1 maintains a set vehicle speed when there is no preceding vehicle, and when it catches up with a preceding vehicle, it follows the preceding vehicle while maintaining a distance according to a predetermined inter-vehicle time (time gear up = inter-vehicle distance / host vehicle speed) that matches the speed of the preceding vehicle. Furthermore, when vehicle 1 catches up with a preceding vehicle that is decelerating and stopping, it decelerates and stops while maintaining a predetermined inter-vehicle distance, and if the preceding vehicle starts moving within the predetermined time, it restarts to match it and continues following.

The engine controller 20, AMT controller 40, brake controller 30, and ACC controller 10 described above are all comprised of a microcomputer (MCU) consisting of a ROM that stores control programs and setting data, a RAM that temporarily stores the results of arithmetic processing, a CPU that performs arithmetic processing, and a communication I/F, and are connected via an in-vehicle network (such as CAN) to a group of sensors including the preceding vehicle detection means 11 so that they can communicate with each other.

(Curve driving assistance function during ACC driving)
The ACC controller 10 has a curve driving assistance function that requests deceleration when it detects that the vehicle is entering a curve with a curvature of a predetermined value or more during ACC driving, in order to control the vehicle to a speed at which the vehicle can travel around the curve stably (curve driving speed).

Means for detecting curves with a predetermined curvature or greater can include known methods such as a yaw rate sensor 12, a steering angle sensor 13, image analysis by a front camera 14, which can also constitute a preceding vehicle detection means 11, matching position information detected by a positioning system 15 (GNSS, navigation system) with map information (curve curvature information), or a combination of these.

For example, when using the yaw rate sensor 12, a lookup table or the like can be prepared in advance in the ROM area that specifies the yaw rate threshold corresponding to the vehicle speed at which stable travel is possible depending on the radius of curvature of the curve. When the yaw rate detected by the yaw rate sensor 12 reaches the yaw rate threshold specified depending on the current vehicle speed, it can be determined that the vehicle is entering a curve with a predetermined curvature or greater. At this time, the yaw rate calculated from the difference in wheel speeds detected by the left and right wheel speed sensors 16, 17 can also be used in combination.

Furthermore, when image analysis from the front camera 14 is used, lane markings (roadside lines, roadside markings) are recognized while the vehicle is traveling, and the curvature of the curve can be estimated by performing coordinate transformation (projection transformation) on the overhead image. When image analysis from the front camera 14 or position information and map information from the positioning system 15 are used, it is possible to detect the curve ahead before entering the curve. Therefore, when approach to a curve is detected by these means, it is possible to start monitoring the curve curvature using the yaw rate sensor 12 and calculating the upper vehicle speed limit for curve travel. The curve detection means described above can also be used to determine the end of curve travel when passing through a curve.

When the curve detection means detects the vehicle entering a curve with a predetermined curvature or greater during ACC driving and the vehicle speed at that time (the ACC set speed or the preceding vehicle following speed) is predicted to exceed the vehicle speed at which stable driving around the curve is possible, i.e., when the curve driving conditions are met, the ACC controller 10 switches to curve driving assistance mode and issues a deceleration request to the engine controller 20 and brake controller 30 to control the vehicle speed to a speed at which stable driving around the curve is possible, regardless of the ACC set speed or the preceding vehicle following speed.

In response to a deceleration request (torque reduction request/brake request) from the ACC controller 10, the engine controller 20 reduces the torque of the engine 2, and if the deceleration request value is equal to or greater than a predetermined value, the brake controller 20 activates the brakes 6, 7. At this time, the deceleration request (torque reduction request) to the engine controller 20 is also shared with the AMT controller 40, which then performs a gear shift operation by referencing a gear shift map based on the current vehicle speed and the torque reduction request value.

As mentioned above, when driving in ACC mode on a flat road with low rolling resistance or on a downhill slope and entering a sharp curve, the required torque value drops to suppress acceleration, causing the vehicle to upshift. However, if the required torque value drops significantly, for example to zero (Nm), the gear may change in two steps in a very short time, impairing the shifting feel.

(First embodiment)
Therefore, in the control according to the present invention, when entry into a curve of a predetermined curvature or greater is detected and the curve driving condition is met, the upper limit of gear changes in the automatic transmission 4 is limited to one gear.

In other words, when the curve driving condition is met (curve driving flag), the ACC controller 10 requests deceleration to assist curve driving, but when the curve driving condition is met, the AMT controller 40 limits upshifting to one gear regardless of the torque request value.

For example, if the AMT controller 40 upshifts one gear in response to a deceleration request in curve driving assistance mode, the ACC controller 10, having received the upshift, will prohibit the AMT controller 40 from further upshifting until the curve driving is completed.

For example, if the vehicle 1 is traveling in fourth gear of the six-speed automatic transmission 4 during ACC driving and enters a curve, and the ACC controller 10 requests deceleration and the vehicle upshifts to fifth gear, an upshift to sixth gear is prohibited until the vehicle has finished traveling around the curve.

This allows the vehicle to immediately shift up to fourth gear in response to an acceleration request (torque increase request) when the vehicle transitions to straight driving after completing a curve or when the vehicle speed limit is relaxed due to a decrease in yaw rate as the curvature of the curve decreases, maintaining good acceleration/deceleration performance and gear change feel.

Second Embodiment
Also, when the curve traveling condition is met, the upper limit of the gear stage change can be limited to one stage only for a predetermined period of time, rather than until the curve traveling ends.

In other words, when the curve driving conditions are met, the AMT controller 40 shifts up one gear in response to a deceleration request for curve driving assistance. At the same time, the ACC controller 10, which has received the shift up, begins timing a predetermined time T1 (e.g., 1 to 2 seconds) and prohibits the AMT controller 40 from further shifting up until the end of this predetermined time T1.

If the curve driving condition is met when the predetermined time T1 has elapsed, the gear change restriction is reset, timing of the predetermined time T1 begins anew, and until that timing ends, the upper limit of gear changes in the automatic transmission 4 is limited to one gear (shifting up by one further gear is permitted).

For example, if the vehicle is traveling in fourth gear of the six-speed automatic transmission 4 during ACC driving and enters a curve, and a deceleration request from the ACC controller 10 causes an upshift to fifth gear, an upshift to sixth gear is prohibited until a predetermined time T1 has elapsed. However, if the deceleration request for the curve continues even after the predetermined time T1 has elapsed, an upshift to sixth gear is permitted. A further predetermined time T1 begins to be counted upon upshifting to sixth gear, and until the predetermined time T1 has elapsed, a downshift to fifth gear is permitted, but a downshift to fourth gear is prohibited. After the further predetermined time T1 has elapsed, a downshift to fourth gear is permitted. In this case, too, two gear changes in an extremely short period of time are prevented, maintaining a good gear change feel.

(Third embodiment)
On mountain roads, etc., there are often repeated curves of a predetermined curvature or greater. Therefore, when the curve driving condition is met and the vehicle transitions to curve driving, a curve driving history is stored, and control can be added to prohibit further gear changes if curve driving is repeated for a predetermined time T2 (for example, 5 to 30 seconds) that is longer than the predetermined time T1.

In other words, when a curve driving condition is first met, a predetermined time T2 is measured in parallel with the measurement of the predetermined time T1, and the curve driving history is maintained until the end of the measurement of the predetermined time T2. If the next curve driving condition is not met during that time, the curve driving history is cleared. On the other hand, if the next curve driving condition is met before the end of the measurement of the predetermined time T2, a new measurement of the predetermined time T2 is performed, and the AMT controller 40 is prohibited from changing gears. This control fixes the gear when curves of a predetermined curvature or greater are repeatedly encountered, thereby avoiding gear changes and providing the advantage of good acceleration and deceleration performance.

(First Example)
Next, an example of the curve running support function during ACC running corresponding to the third embodiment will be described with reference to the flowchart of FIG. 2 and FIG.

First, at time t1, the vehicle is traveling in fourth gear through curve section Z1, but because the curvature does not meet the predetermined curvature, the ACC controller 10 only performs speed control to maintain the set vehicle speed (step 100).

After that, even after time t2, when the vehicle enters straight section Z2, speed control continues to maintain the set vehicle speed. However, at time t2', a curve section Z3 with a predetermined curvature or greater is detected ahead on the road, and if the curve driving condition is met at time t3 (step 110; YES), the ACC controller 10 refers to the curve driving history (step 112). If there is no curve driving history within the predetermined time T2 (step 112; YES), the ACC controller 10 requests deceleration to reduce the vehicle speed to a level that allows stable driving on curve section Z3, and simultaneously limits the gear change to an upper limit of one gear (step 113).

In response to a deceleration request (torque reduction request) from the ACC controller 10, the AMT controller 40 upshifts to fifth gear, but because gear changes are limited to an upper limit of one gear during the predetermined time T1, upshifts to sixth gear are not performed (step 113).

After that, at time t4 after passing through a curve (t3'), a straight section Z4 is detected and the curve end condition is met (step 114; YES), the upper limit one gear shift restriction is released (step 120), and a downshift to fourth gear is performed in response to an acceleration request (torque increase request) with the set vehicle speed as the target vehicle speed, and acceleration begins. However, the measurement of the predetermined time T2 from time t3 continues, and the curve driving history due to the curve section Z3 condition being met is maintained.

The vehicle then travels along a short straight section Z4, and at time t4', a curve section Z5 with a curvature of at least a predetermined value is detected ahead on the road. If the curve driving condition is met at time t5, before the predetermined time T2 has elapsed (step 110; YES), the ACC controller 10 references the curve driving history (step 112). Since there is a curve driving history within the predetermined time T2 (step 112; NO), the ACC controller 10 issues a deceleration request to reduce the vehicle speed to a level that allows stable travel through the curve section Z5, and simultaneously prohibits gear changes (step 115). Accordingly, the vehicle is fixed in fourth gear while traveling through the curve section Z5.

Thereafter, after traveling around a curve, a quasi-straight section Z6 is detected at time t6, and when the curve end condition is met (step 116; YES), the speed change restriction is released (step 120). However, since the gear position was fixed to fourth speed while traveling around the curve, acceleration is immediately started in response to an acceleration request (torque increase request) with the set vehicle speed as the target vehicle speed. However, the measurement of the predetermined time T2 from time t5 continues, and the curve traveling history for the curve section Z5 is maintained.

Then, after traveling through the quasi-straight section Z6 and a predetermined time T2 has elapsed, the curve driving history for the curve section Z5 is cleared.

In addition, if the vehicle comes to a stop while traveling through a curve, the curve end condition is met and the speed change restriction is released. Furthermore, since the curve driving assistance function operates on the premise of ACC driving, if the ACC function is overridden by the driver's intervention in braking or accelerator operation, the speed change restriction is released and the curve driving assistance function is also stopped.

In the first example (third embodiment) described above, the timing of the predetermined time T2 for retaining the curve driving history begins when the curve driving condition is met. However, it is also possible to start timing the predetermined time T2 (T2') when the curve section is passed and the curve driving end condition is met.

Furthermore, instead of prohibiting gear changes when curves are repeated within the predetermined time T2 (T2'), a switch that can be manually operated by the driver, such as a mountain road mode switch, can be set, and when this mountain road mode switch is turned on and mountain road mode (gear change prohibited mode) is specified, gear changes can be immediately prohibited when curve driving conditions are met.

(Second Example)
FIG. 3 is a flowchart showing a second embodiment of the curve driving support function including the mountain road mode switch, and will be described with reference to FIGS.

When the mountain road mode switch is turned on (step 101; YES) during ACC driving (step 100), for example, while driving in fourth gear on a straight section Z2, if a curve section Z3 with a predetermined curvature or greater is detected ahead at time t2' and the curve driving condition is met at time t3 (step 102; YES), the ACC controller 10 will issue a deceleration request to reduce the vehicle speed to a level that allows stable driving on the curve section Z3, and will also prohibit gear changes (step 103). As a result, the gear is fixed at fourth gear while driving on the curve section Z3.

After that, at time t4, straight section Z4 is detected and the curve end condition is met (step 104; YES), and the speed change restriction is released (step 120). However, because the gear position was fixed at fourth gear, acceleration is immediately initiated in response to an acceleration request (torque increase request) with the set vehicle speed as the target vehicle speed.

Then, the vehicle travels along a short straight section Z4, and at time t4', a curve section Z5 with a predetermined curvature or greater is detected ahead on the road. If the curve travel condition is met at time t5 (step 102; YES), the ACC controller 10 requests deceleration to reduce the vehicle speed to a level that allows stable travel along the curve section Z5, and simultaneously prohibits gear changes (step 103).

In this way, when the mountain road mode switch is turned on, if the vehicle enters a curve with a curvature of a specified value or greater while driving in ACC, gear changes while driving on the curve are prohibited, which has the advantage of avoiding gear changes while driving on the curve and providing good acceleration and deceleration performance.

In particular, in a vehicle 1 equipped with an AMT-type automatic transmission 4, shifting involves instantaneous torque control linked to clutch engagement and disengagement, so by fixing the gear position while driving around a curve, a good feeling is maintained when driving around a curve, and there is the advantage that ACC driving suitable for AMT vehicles, which have high power transmission efficiency when the clutch is engaged, can be performed.

In the above embodiment, the curve assistance function was described for a vehicle equipped with an ACC function. However, the present invention can also be implemented as a curve assistance function for a vehicle equipped with an LKA (Lane Keeping Assist) function that recognizes the vehicle's driving lane using forward detection means such as the forward camera 14 or preceding vehicle detection means 11, and performs automatic steering or steering assistance to keep the vehicle within the lane, or for a vehicle equipped with an ADAS (Advanced Driver Assistance System) that combines an ACC function (vehicle length control) and an LKA function (vehicle width control).

Although several embodiments of the present invention have been described above, it should be noted that the present invention is not limited to the above embodiments, and various modifications and variations are possible based on the technical concept of the present invention.

REFERENCE SIGNS LIST 1 vehicle 2 engine 3 clutch 4 automatic transmission 10 ACC controller 11 preceding vehicle detection means 12 yaw rate sensor 13 steering angle sensor 14 forward camera 15 positioning system 16, 17 wheel speed sensor 20 engine controller 30 brake controllers 36, 37 brakes 40 AMT controller

Claims (5)

A control device for a vehicle equipped with a stepped automatic transmission,
an ACC function that drives the vehicle at a set vehicle speed when there is no preceding vehicle in the vehicle's lane, and requests acceleration/deceleration to follow the preceding vehicle while maintaining a set inter-vehicle time when there is a preceding vehicle in the vehicle's lane;
a curve driving support function that issues a deceleration request when the curve detection means detects that the vehicle is entering a curve with a curvature of a predetermined value or more and a curve driving condition is met; and
In those having
a control device for a vehicle configured to limit an upper limit of gear shifting of the automatic transmission to one gear when the curve driving condition is met while the vehicle is traveling using the ACC function. 2. The vehicle control device according to claim 1 , wherein the control device is configured to start timing a first predetermined time when the curve driving condition is met, and to reset the restriction on gear position change when the curve driving condition is met after the first predetermined time has elapsed. If the curve driving condition is met, the curve driving history is stored, and then:
(i) if the next curve driving condition is not met within a second predetermined time, clear the curve driving history;
(ii) A vehicle control device as described in claim 1 , characterized in that if the next curve driving condition is met within a second predetermined time, the curve driving history is stored, and thereafter, gear changes are prohibited until the curve end condition is met . The vehicle control device of any one of claims 1 to 3 is configured to prohibit gear changes when the curve driving condition is met, when the gear change prohibition mode is designated by turning on a manually operable switch. The vehicle control device of any one of claims 1 to 4, wherein the automatic transmission is an AMT-type automatic transmission equipped with a clutch that transmits engine output to a transmission mechanism, a clutch actuator that engages and disengages the clutch, a shift actuator that changes the gear position of the transmission mechanism, and an AMT controller that controls the shift actuator and the clutch actuator to change the gear position.